Tests of Pulmonary Function

Question 1

For restrictive disease, What happens to maximum flow rate?

Answer 1

it’s reduced

Question 2

What happens to the FEV1 and FVC? The ratio?

Answer 2

FEV1 and FVC both decrease, so the ratio stays pretty much normal

Question 3

What happens to maximum flow rate in obstructive lung disease?

Answer 3

it’s reduced

Question 4

What happens to FEV1 with increased airway resistance? How about with decreased elastic recoil of the lung?

Answer 4

It will be reduced by both

Question 5

What are two ways funcitonal residual capacity can be measured?

Answer 5

He dilution or N2 washout

Question 6

As a review, how can we use the fick principle to measure pulmonary blood flow?

Answer 6

amount of O2 used / ([O2]arterial - [O2]venous)

Question 7

How do we measure ventilation-perfusion rlationships

Answer 7

radioactive xenon

Question 8

What is a normal alveolar to arterial gradient?

Answer 8

small - around 4 mmHg

Question 9

What equation do we use to tell if there’s an inequality of ventilation-perfusion ratios?

Answer 9

the alveolar gas equations:

expected pAO2 = pIO2 - (pCO2/R)

Question 10

WHat are the 4 general causes of hypoxemia?

Answer 10

hypoventilation
diffusion barrier
shunt
ventilation-perfusion mismatch

Question 11

What are the two general causes of hypercapnea?

Answer 11

hypoventilation

V-Q mismatch

Question 12

How can we measure lung compliance?

Answer 12

having subjects swallow an esophageal pressure transducer and measuring pressure changes corresponding to exhaled volume

Question 13

How can we measure airways resistance?

Answer 13

using a body plethysmograph while measure air flow:

inspiration causes a pressure change within the box so you can calculate the volume change from the rpessure change. Can also calculate change in alveolar pressure form the change in volume

Resistance is just the chang in pressure over airflow

Question 14

How can we meausre closing volume?

Answer 14

N2 washout

maximal inhalation of 100% oxygen and then a maximal exhalation during which N2 is measured

Question 15

What are the four phases of N2 measurement in the washout?

Answer 15

1. pure dead space - flat wiht no N2
2. Mixture of dead space and alveolar ventilation - N2 rises
3. Pure alveolar ventilation - flat with 30-40% N2
4. Spike in N2 concentration at the end of expiration

Question 16

What is the N2 spike at the end of expiration caused by?

Answer 16

preferential emptying of the apical regions of the lung

Question 17

How can we measure chemoreceptor responiveness?

Answer 17

have a subject rebreathe into a bag - you have to keep oxygen content contstant if checking for carbon diozide responsiveness and must keep carbon diozide content constant if checking for oxygen repsonsiveness.

Their ventilation rate should go up (?)